Plastic closure with compression molded barrier liner

ABSTRACT

A plastic closure that includes a cap having a base with a peripheral skirt defining a cap interior and threads on the skirt for securing the closure to a container. A liner is secured to the interior of the cap, preferably by compression molding in situ. The liner preferably consists essentially of a blend of matrix polymer material, particulate barrier polymer material and compatibilizer material. The heat and pressure of compression forms the particles of barrier polymer material into platelets that are oriented essentially parallel to the plane of the closure base.

[0001] This application is a division of application Ser. No. 08/997,871filed Dec. 24, 1997.

[0002] The present invention is directed to plastic container closuresfor beverage, food, juice, pharmaceutical and like applications, andmore particularly to an improved process for providing closures withsealing liners having transmission resistance to gases, water vaporand/or flavorants (flavor scalping).

[0003] Reference is made to application Ser. No. 08/998,072 filed Dec.24, 1997, entitled “Plastic Closure with Compression MoldedSealing/Barrier Liner” and assigned to the assignee hereof.

BACKGROUND AND OBJECTS OF THE INVENTION

[0004] It has heretofore been proposed to provide a plastic closure fora container that comprises a plastic cap with an interior liner forsealing engagement with the sealing surface of the container. Forexample, U.S. Pat. No. 4,984,703 discloses a plastic closure thatcomprises a cap having a base with a peripheral skirt and threads forsecuring the cap to a container, and a sealing liner compression moldedin situ on the interior of the cap base. The sealing liner comprises ablend of ethylene vinyl acetate (EVA) and a thermoplastic elastomericmaterial such as olefin or styrene-butadiene-styrene. U.S. Pat. No.5,451,360 discloses a method and apparatus for compression molding theliners in situ within the caps.

[0005] It has also heretofore been proposed to form a barrier liner fora plastic closure in an injection or extrusion molding operation from ablend of a thermoplastic olefin homopolymer or copolymer such as ethylvinyl acetate (EVA) or thermoplastic elastomer, and a barrier polymer tooxygen and carbon dioxide transmission such as ethyl vinyl alcohol(EVOH). The blend also typically includes a compatiblizer material topromote adhesion between the EVOH particles and the EVA carriermaterial. In general, particles of the EVOH barrier material force gasesthat permeate the EVA carrier either to follow a tortuous path aroundthe EVOH particles or permeate through the EVOH polymer, thus slowingthe rate of gas transmission. The EVOH particles are generallyspheroidally dispersed in the EVA carrier since these materials are notmiscible. As a general proposition, the percentage reduction in gastransmission corresponds to the percentage content of EVOH in the blend.The results of this technology to date have not provided high barrierproperties at acceptable cost and sealing performance.

[0006] It is therefore a general object of the present invention toprovide a liner for a plastic closure that combines the functions of aseal for engagement with the container sealing surface and an improvedbarrier against gas transmission, flavor absorption (flavor scalping)and/or water vapor permeation. Another and more specific object of thepresent invention is to provide a liner of the described character thatis of readily moldable and inexpensive composition. Yet another objectof the invention is to provide a liner that satisfies the foregoingobjectives and is of clear or translucent construction to permit readingthrough the liner of printing on the closure. A further object of thepresent invention is to provide a method of fabricating such a liner,and a plastic closure embodying such a liner.

SUMMARY OF THE INVENTION

[0007] In accordance with one aspect of the present invention, there isprovided a plastic closure that comprises a cap having a base with aperipheral skirt defining a cap interior and means on the skirt forsecuring the closure to a container. A liner is secured to the interiorof the cap, preferably by compression molding in situ. The linerconsists essentially of a blend of a matrix polymer, a barrier materialand a compatibilizer. The barrier material is in the form of adiscontinuous distributed phase of particles in a continuous matrixphase. It has been found that the heat and pressure of compressionmolding forms the barrier polymer particles into thin overlappingsubstantially two-dimensional platelets that are oriented within thematrix polymer essentially parallel to the plane of the liner. Thus, gasthat permeates the liner must follow a more tortuous path around theplatelets, which greatly increases barrier efficiency.

[0008] The “matrix polymer” is a thermoplastic elastomer, a soft olefinpolymer, or a combination thereof. A thermoplastic elastomer is asynthetic polymer having the processability of a thermoplastic materialand the functional performance and properties of a conventionalthermoset rubber. There are six generic classes of thermoplasticelastomer commercially available, including styrenic block copolymers(SBC), polyolefin blends (TPO), elastomeric alloys, thermoplasticpolyurethanes (TPU), thermoplastic copolyesters and thermoplasticpolyamides. Thermoplastic elastomers are described beginning at page 64in Modern Plastics Encyclopedia Handbook, published by McGraw-Hill,1994, the disclosure of which is incorporated by reference. Examples ofthermoplastic elastomers are styrene block copolymers as manufactured byShell Chemical under the trademark KRATON. These synthetic polymersconsist of three discrete blocks of the linear or A-B-A type:styrene-butadiene-styrene, styrene-isoprene-styrene, andstyrene-ethylene/butylene-styrene-styrene. An elastomeric alloy isethylene-propylene-diene terpolymer (EPDM). Another elastomeric alloyconsists of compounds of EPDM/PP and butyl rubber/PP as manufactured byAdvanced Elastomer Systems under the tradenames SANTOPRENE and TREFSINand disclosed in U.S. Pat. Nos. 4,130,535, 4,311,628, 4,130,534 and4,607,074. In general, thermoplastic elastomers are characterized by aShore A hardness of 45 to 95 and a flexural modulus of 30,000 to 100,000psi.

[0009] Soft olefin polymers are thermoplastic olefins, homopolymers andcopolymers which are flexible, elastic with a Shore A hardness of lessthan about 100. Typical soft olefin polymers are: metallocene-madepolyethylene, ethylene-propylene rubbers, ethylene copolymers and blendsthereof, ethylene copolymers such as ethylene vinyl acetate, ethylenemethyl acrylate copolymers and ionomers, and combinations thereof.Examples of soft olefin polymers are alpha olefin substitutedpolyethylenes manufactured using single site catalyst technology (thesematerials are known in the art as metallocene-made polyethylenes);ethylene vinyl acetate (EVA) such as manufactured by DuPont under thetrademark ELVAX; polypropylene made with single site catalyst technologyknown in the art as metallocene-made polypropylenes; syndiotacticpolypropylenes as marketed by Fina Oil and Chemical; ethylene/propylenecopolymers and styrene-ethylene interpolymers as marketed by DowChemical; and ionomers such as DuPont's SURLYN product line.

[0010] The matrix polymer is typically compounded with anti-oxidants,lubricants and other stabilizing materials, as known in the art.

[0011] A “compatibilizer” is a thermoplastic that ties two otherthermoplastics together by a reactive (covalent or dipole-dipole) bondor a non-reactive (chain entanglement) means. Examples include maleicanhydride grafted polymers or ethylene vinyl acetate grafted polymerssuch as Quantum Chemical's PLEXAR (trademark), Mitsui Petrochemical'sADMER (trademark) and DuPont's BYNEL (trademark) product lines, ethylenemethyl acrylate, and ionomers.

[0012] A “barrier material” is a thermoplastic material that has a lowgas and/or water vapor transmission rate, and presents a high barrier toodorants and essential oils. The following materials have gastransmission rates lower than EVA, which is an industry standard linermaterial: EVOH (ethylene vinyl alcohol) such as Nippon Goshei's SOARNOLproduct line and Evalca's EVAL (trademark) product line, nylons such asDupont's SELAR (trademark) PA, EMS's G21 and Mitsubishi Gas' MXD6product lines, British Petroleum's BAREX (trademark) acrylonitrileproduct line, blends of EVOH and amorphous nylon, blends of EVOH and anionomer such as SURLYN (DuPont), and cyclic olefin copolymers such asmarketed by Ticona. Other suitable barrier materials and blends aredisclosed in U.S. Pat. Nos. 4,977,004 and 5,064,716, the disclosures ofwhich are incorporated herein by reference.

[0013] It is currently preferred that the liner also include an additivefor reducing the coefficient of friction between the liner and thesealing surface of the container. In the art these additives are called“lubricants.” Typical additive lubricants include fatty acid amides, andfatty acid esters, microcrystalline waxes and polyethylene glycols. Apreferred lubricant is a low molecular weight fatty acid amide materialthat blooms to the exposed surface of the polymer material upon coolingfrom the melt state, thereby reducing the coefficient of frictionbetween the liner and the container sealing surface. Examples are:primary amides with the general chemical structure R—CO—NH2, where R isan alkyl group; secondary amides with the general chemical structureR—CO—NH—R′; where R, R′ are alkyl groups; secondary bis-amides with thegeneral chemical structure R—CO—NH—A—NH—CO—R, where R, R′ are alkylgroups and A is an Y alkylene group; and blends of the above materialssuch as in U.S. Pat. No. 5,306,542. The lubricant preferably comprisesabout 0.5% to 2.0% of the total liner composition by weight, mostpreferably about 1% by weight. The lubricant is preferably compoundedinto thermoplastic elastomer material (along with any desired colorants)by the material manufacturer. The amount of lubricant and/or colorant isnot included in the calculations of compositions in this application.

[0014] In the currently preferred blends of matrix polymer, barriermaterial and compatibilizer, the barrier material is in the range ofabout 20% to 60% by weight, the compatibilizer in the range of about 1%to 10% by weight, and the balance consists essentially of the matrixpolymer (with lubricant). The relative component percentages will varywith applications, and will depend upon hardness and thereforesealability, the ability of the barrier material to form platelets inthe matrix polymer, and desired removal torque. As to hardness, it hasbeen found that a liner hardness higher than about 94 to 95 Shore (A) istoo hard for proper sealing with the container. When employing anelastomer that is relatively hard, such as EVA, the upper limit of thebarrier material may be relatively low, such as 35% EVOH. However, whenemploying a matrix polymer of relatively low hardness, such asthermoplastic elastomer, the upper limit of the barrier material may bemuch higher, such as 50% to 60% EVOH.

[0015] It has also been found that the amount of barrier material thatcan be included in the blend also depends in part upon polarity of thematrix polymer. Miscibility of the barrier material in the matrixmaterial decreases with decreasing polarity of the matrix material,which means that higher percentages of barrier material can be blendedwith matrix polymers of lower polarity while still maintaining adiscontinuous barrier platelet phase. The amount of compatibilizer alsoaffects the ability of the barrier material to form platelets. Aboveabout 10% compatibilizer, the barrier material becomes too well mixedwith the matrix polymer to form the platelets that characterize theinvention. Below about 1%, the liner does not exhibit good mechanicalproperties and does not bond properly with the closure shell.

[0016] In accordance with another aspect of the present invention, thereis therefore provided a method for making a liner for a plastic closurethat comprises the steps of forming a pellet that consists essentiallyof a blend of a thermoplastic elastomer, a polymer having high barrierproperties and a compatibilizer to promote adhesion between theelastomer and the barrier polymer and between the liner and the closureshell. The pellet is then compression molded, preferably within aclosure shell, to form a liner disk bonded to the closure shell, andwithin which the heat and pressure from compression molding forms thebarrier polymer into platelets that are oriented essentially parallel tothe plane of the disk. The resulting liner exhibits greatly lowered gastransmission rate as compared with a liner formed of a similar blend inother than a compression molding operation.

[0017] In accordance with a third aspect of the invention, there isprovided a sealing liner for a plastic closure that comprises a diskthat consists essentially of a matrix polymer within which a dispersionof platelets of a barrier material to gas transmission are disposedessentially in planes parallel to the disk. The sealing liner preferablyis compression molded in situ within a plastic closure from acompression mold charge or pellet in which the matrix polymer, thebarrier material and a compatibilizer are blended such that the barriermaterial consists of discrete particles that are flattened intoplatelets during the compression molding operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention, together with additional objects, features andadvantages of thereof, will be best understood from the followingdescription, the appended claims and the accompanying drawings in which:

[0019]FIG. 1 is a schematic diagram that illustrates compression moldingof barrier liners in a plastic closure in accordance with a presentlypreferred implementation of the invention;

[0020]FIG. 2 is a diametrically sectioned elevational view of a plasticclosure with integral barrier liner manufactured in accordance with theprocess schematically illustrated in FIG. 1;

[0021]FIGS. 3A and 3B are photomicrographs at 50× of portions of theliner within the circles 3A and 3B in FIG. 2;

[0022]FIG. 3C is a photomicrograph at 100× of the portion of the linerillustrated in FIG. 3B;

[0023]FIG. 4 is a photomicrograph at 100× of a charge pellet;

[0024]FIG. 5A is a photomicrograph at 50× of the edge portion of anotherembodiment of the invention;

[0025]FIG. 5B is a photomicrograph at 100× of the center portion of theliner illustrated in FIG. 5A; and

[0026]FIGS. 6 and 7 are views similar to that of FIG. 2 but showingmodified liner geometries.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027]FIG. 1 is a schematic diagram of a process 10 for manufacture ofplastic closures in accordance with the present invention. An extruder12 has a hopper 14 for receiving starting materials. The output ofextruder 12 is fed to a pellet slicer 16 from which individual chargepellets 20 are provided. Charge pellet 20 is placed within aprefabricated plastic closure cap 22 in the female die 24 of acompression mold 26. A male die section 28 is closed against pellet 20,cap 22 and die 24 so as to compression mold pellet 20 into a liner thatis welded or bonded to the interior surface of the cap base. That is,referring to FIG. 2, the charge pellet is compression molded in situagainst the base 30 of cap 22 so as to form a liner 20 a. This may beaccomplished by hand, or more preferably with the machine disclosed inthe above-noted U.S. Pat. No. 5,451,360. Cap 22 also includes a skirt 32that axially extends from the periphery of base 30, having internalthreads 34 for securing cap 22 to a container. Alternatively, pellet 20may be separately compression molded to form liner 20 a, which may thenbe adhesively secured within cap 22 against base 30. Such an operationrequires additional steps and expense, and is therefore not preferred.As a second alternative, the liners may be formed in the closures asdisclosed in U.S. Pat. No. 4,518,336. See also U.S. Pat. Nos. 3,674,393,3,702,148, 3,877,497 and 4,518,336. FIG. 6 illustrates an alternativeliner 20 b having a flat geometry, as opposed to the liner 20 a of FIG.3 having a thickened periphery. FIG. 7 illustrates a liner 20 c having aflat periphery and a thickened mid section for holding additionalbarrier material.

[0028] For manufacture of plastic closure barrier liners in accordancewith the presently preferred implementation of the invention, the inputto extruder 12 at hopper 14 preferably consists essentially of one ormore barrier polymers, one or more matrix polymers (preferablypreblended with lubricant and any desired colorants), and one or morecompatibilizer materials. The input materials are mixed and blended inhopper 14. The barrier polymer input preferably is selected from thegroup consisting of EVOH, nylon, acrylonitrile copolymers such asstyrene acrylonitrile and acrylonitrile methylacrylate, blends of EVOHand amorphous nylon, blends of EVOH and an ionomer, acrylonitrile,cyclic olefin copolymers, and blends thereof. The matrix polymer inputto hopper 14 preferably is selected from the group consisting of EVA,ethylene/propylene copolymers, styrene block copolymers, terpolymers,ionomers, thermoplastic rubbers, styrene/ethylene/butadiene/styreneblock copolymers, styrene/ethylene/butadiene/styrene compounds,styrene/butadiene/styrene block copolymers, EPDM, metallocene-madelinear low polyethylene, metallocene-made syndiotatic polypropylene,rubbers such as butyl rubber, styrene copolymers such asstyrene/ethylene and terpolymers such as styrene/ethylene/butylene,polypropylene/butyl rubber, and blends thereof. The compatibilizer inputto hopper 14 preferably is selected from the group consisting of maleicanhydride grafted polymers, ethylene vinyl acetate grafted polymers,EVA, ethylene methyl acrylate, ionomers and blends thereof. As notedabove, a lubricant selected from the group consisting of primary amides,secondary amides, secondary bis-amides and blends thereof, preferably ispreblended with the matrix polymer.

[0029] In the current invention, the liner material consists of aheterogeneous blend of a matrix polymer (TPE or soft olefin) and acondensation polymer or barrier polymer, a compatibilizer andappropriate lubricant. In the disclosed examples of the invention, thematrix polymer is ethylene vinyl acetate (EVA) marketed under thetrademark ELVAC 650 by Dupont), the barrier polymer is ethylene vinylalcohol (EVOH marketed under the trade designation E105B by Evalca), andthe compatibilizer is a maleic anhydride grafted polypropylene (ADMERQF551) with 0.5% by weight erucamide +0.5% ethylene bis-oleamide as thelubricant. Although it is not required, it is preferred that all thecomponents Of the liner be used in particulate form and the componentsmixed as particulates prior to extrusion. The particles should as ageneral rule, be of a size such that the molten blend of incompatiblepolymers exhibit the heterogeneity necessary to achieve the barrierproperties that characterize the invention. When the particles are oftoo small a size or the blend is too well mixed, the compound willfunction as a homogenous composition with little oxygen barrierproperties.

[0030] It is preferable that the input to extruder 12 be substantiallyuniformly blended, and that the output of extruder 12 be ofsubstantially uniform composition. Substantial uniformity of compositionis important in achieving a uniformity of properties. The barrierparticles should be uniformly distributed—i.e., statisticallyhomogeneously distributed—to achieve desired barrier properties.Extruder 12 should be a low-shear low-mixing extruder to avoidhomogenization of the mixture in which the particles or domains of thediscontinuous phase are too small.

[0031] It has been found to be desirable that the barrier material notbe too well blended into the matrix polymer. The barrier material shouldbe in the form of discrete particles, essentially spheroidal, in thecharge pellet, as illustrated in FIG. 4. If the barrier material is toowell blended into the elastomer, there are no discrete particles in theelastomer matrix to form platelets during comparison molding. FIGS. 3A,3B and 3C are photomicrographs of the center (FIGS. 3B and 3C) and edge(FIG. 3A) portions of liner 20 a (FIG. 2) formed of a blend of 65% EVA,34% EVOH and 1% compatibilizer (a maleic anhydride grafted polymer). Thebarrier material is essentially in the form of thin flat overlappingsubstantially two-dimensional platelets (dark in the micrographs)parallel to the plane of the liner. It is believed that the force ofcompression molding, coupled with the radial material flow duringcompression molding, forms and aligns these platelets parallel to theplane of the liner disk. FIG. 5A and 5B are similar photomicrographs ofanother liner compression molded from the same material blend.

[0032] Several sets of test samples were fabricated in the form ofliners compression molded into closures. The test materials wereextruded through the system of FIG. 1 at a melt temperature of 430 to450° F. in proportions to yield the desired weight ratios. Pellets 20were manually cut from the extrudate and placed in closure shells 22.With the pellets 20 still at or near melt temperature, the closure andpellet were placed in a compression mold as in FIG. 1, and thecompression tool was activated to compress the pellet. The linercompression molding machine was that disclosed in above-noted U.S. Pat.No. 5,451,360. The liners were molded to the configuration of FIG. 2,with a thickness at position 3A of 0.025 to 0.028 inches, and athickness at position 3B of 0.015 to 0.018 inches. All closures were 43mm closures, and all liners had a diameter of 1,539 inches. The closureswere conditioned for about two weeks at 100% relative humidity prior tofurther testing.

[0033] Each test closure with liner was then threaded onto a PET bottlefinish at industry standard application torque (25 to 30 inch-pounds fora 43 mm closure). The finish was then cut from the bottle and epoxiedonto a metal plate surrounding a hole coupled to a purge tube. The platewith closure was then placed in a Mocon OXYTRAN oxygen permeabilitytester. Oxygen outside of the closure was maintained at 1 atm, 23° C.and 100% relative humidity, and nitrogen gas was used to purge thevolume within the closure to measure oxygen concentration, and thereforeoxygen permeation through the closure. When oxygen permeability reachsteady state, the figure was multiplied by 0.21 to correct for thequantity of oxygen in the atmosphere, and recorded.

[0034] When employing EVOH in polymer blends, it has generally beenfound in the past that the percentage reduction of gas transmissionroughly corresponds to the percentage of EVOH in the blend. For example,a blend having 20% EVOH would typically be expected to exhibit a 20%reduction in oxygen transmission as compared with the same linercomposition without EVOH. However, it was surprisingly discovered whenimplementing the present invention that the reduction in oxygentransmission rate far exceeds the percentage of EVOH in the test blends.For example, a polypropylene cap having an in-situ compression-moldedbarrier liner, in which the liner consists of a blend of 65% EVA, 34%EVOH and 1% adhesive/compatibilizer by weight, had an oxygentransmission rate of 0.006 to 0.007 cc/43 mm closure/day, as comparedwith a rate of 0.013 cc/43 mm closure/day for an identical closurehaving a compression molded EVA liner of the same thickness and testedunder identical conditions. Another test was performed on closures withcompression molded liners consisting of 79% EVA, 20% EVOH and 1%compatibilizer. These samples exhibited an oxygen transmission rate of0.010 cc/43 mm closure/day, again as compared with a rate of 0.013 cc/43mm closure/day for comparable EVA liners.

[0035] Other tests were performed on liners compression molded into a 43mm diameter polypropylene closures having a liner diameter of 1.539inches. These tests were performed at 100% relative humidity. All linerswere 0.015 inches thick: TABLE 1 Oxygen Transmissivity Test Sample(cc/43 mm closure/day) (1) 100% EVA 0.013 (2) 79% EVA, 20% EVOH, 0.0101% comp. (3) 65% EVA, 34% EVOH, 0.007 1% comp. (4) 65% EVA, 34% EVOH,0.010 1% comp.

[0036] The compatibilizer in samples (2) to (4) was the maleic anhydridegrafted polymer previously noted. Test sample (4) was too well mixed,and thus did not exhibit the good results of sample (3). Samplehardnesses are illustrated by the following table: TABLE 2 MaterialHardness (Shore A) 100% EVA  91  75% EVA/25% EVOH  92-94  50% EVA/50%EVOH  94-96  25% EVA/75% EVOH  97 100% EVOH 100+

[0037] As noted above, the amount of barrier material that can beemployed in the blend depends in part on the hardness of the matrixpolymer. For example, the following table compares the hardnesses andability to seal against a container mouth for various mixtures of EVOHwith EVA (hardness equals 91 Shore A) and polypropylene/butyl rubber(TREFSIN, hardness equals 65 Shore A). The maleated polypropylenecompatibilizer and lubricant were employed in the same amounts in allsamples. TABLE 3 Hardness Material (Shore A) Functional Sealing EVA +20% EVOH 92 Yes EVA + 34% EVOH 92 Yes EVA + 50% EVOH 94 NoPolypropylene/butyl 67 Yes rubber + 20% EVOH Polypropylene/butyl 75 Yesrubber + 34% EVOH Polypropylene/butyl 81 Yes rubber + 50% EVOH

[0038] The polypropylene/butyl rubber employed is marketed by AdvancedElastomer Systems under the trademark TREFSIN. Thus, a greater quantityof barrier material can be incorporated into a softer matrix materialwhile maintaining the ability to function as a seal.

[0039] There have thus been disclosed as barrier liner, a closure withbarrier liner, and a method of manufacturing the same, that fullysatisfy the objectives and aims previously set forth. The liner isreadily manufactured from otherwise conventional materials, andemploying otherwise conventional techniques and equipment. The linerprovides improved efficiency, in terms of the quantity of barriermaterial employed versus permeation and transmission of gasses such asoxygen and carbon dioxide, water vapor, and essential flavor oils(flavor scalping). Specific barrier material combinations have beendisclosed. Other combinations are envisioned for different applications,and will suggest themselves to persons of ordinary skill in the artbased upon the principles and parameters herein discussed. All patentsand/or publications cited above are incorporated herein by reference.

1. A method of making a plastic closure that comprises the steps of: (a)providing a plastic cap that includes a base and a peripheral skirtdefining a cap interior, (b) placing within said cap interior, on saidbase, a mold charge that includes a blend of matrix polymer material andbarrier polymer material, and (c) compression molding said mold chargein situ within said cap interior against said base to form a linerhaving said barrier polymer material in the form of discrete overlappingplatelets within said matrix polymer material and oriented essentiallyparallel to said base.
 2. The method set forth in claim 1 wherein saidstep (b) is such that said mold charge includes a blend of said matrixpolymer material, said barrier polymer material, and a compatibilizerresin material to promote adhesion between said matrix polymer materialand said platelets.
 3. The method set forth in claim 2 wherein said moldcharge consists essentially of said matrix polymer material, saidbarrier polymer material and said compatibilizer resin material.
 4. Themethod set forth in claim 3 wherein the amount of said barrier polymermaterial is in the range of about 20% to 60% by weight, saidcompatibilizer resin material is in the range of about 1% to 10% byweight, with the balance consisting of said matrix polymer material. 5.The method set forth in claim 1 further including, prior to said step(b): (d) extruding mold charge material having said matrix and barrierpolymer materials therein, and (e) severing said mold charge from saidmaterial extruded in said step (d) for placement in said cap in saidstep (b).
 6. The method set forth in claim 1 wherein said matrix polymermaterial is selected from the group consisting of thermoplasticelastomers, soft olefin polymers, and mixtures thereof.
 7. The methodset forth in claim 6 wherein said matrix polymer material is athermoplastic elastomer having a Shore A hardness of 45 to 95 andflexural modulus of 30,000 to 100,000 psi.
 8. The method set forth inclaim 6 wherein said matrix polymer material is a thermoplasticelastomer selected from the group consisting of styrene block copolymersand elastomeric alloys.
 9. The method set forth in claim 6 wherein saidmatrix polymer material includes a olefin polymer that is selected fromthe group consisting of metallocene-made polyethylene,ethylene-propylene rubbers, ethylene copolymers, and mixtures thereof.10. The method set forth in claim 1 wherein said barrier polymermaterial is selected from the group consisting of EVOH, nylon,acrylonitrile copolymers, blends of EVOH and amorphous nylon, blends ofEVOH and an ionomer, acrylonitrile, cyclic olefin copolymers, and blendsthereof.
 11. The method set forth in claim 1 wherein said step (b) issuch that said mold charge includes compatibilizer material selectedfrom the group consisting of maleic anhydride grafted polymers, ethylenevinyl acetate grafted polymers, ethylene methyl acrylate, ionomers andblends thereof.
 12. The method set forth in claim 1 wherein said barrierpolymer material comprises EVOH and said matrix polymer materialcomprises EVA or polypropylene/butyl rubber.
 13. The method set forth inclaim 1 wherein said platelets are substantially uniformly distributedthroughout said liner.
 14. The method set forth in claim 1 wherein saidliner contains lubricant in the amount of about 0.5% to 2.0% by weight.15. The method set forth in claim 14 wherein said lubricant is in theamount of a bout 1% by weight.
 16. The method set forth in claim 14wherein said lubricant is selected from the group consisting of fattyacid amides, fatty acid esters, microcrystalline waxes, polyethyleneglycols, primary amides, secondary amides, secondary-bis amides, andblends thereof.
 17. A method of making a plastic closure that comprisesthe steps of: (a) extruding plastic mold charge material that consistsessentially of a blend of matrix polymer material, barrier polymermaterial and compatibilizer resin material to promote adhesion betweensaid matrix and barrier polymer materials by reactive bonds ornon-reactive adhesion mechanisms, (b) severing a mold charge pellet fromthe mold charge material extruded in said step (a), (c) providing aplastic cap that includes a base and a peripheral skirt defining a capinterior, (d) placing said mold charge pellet within said cap interior,and (e) compression molding said mold charge pellet against said base toform a liner on said base having said barrier polymer material dispersedas overlapping platelets within said matrix polymer material andoriented essentially parallel to said base.
 18. The method set forth inclaim 17 wherein said matrix polymer material is selected from the groupconsisting of thermoplastic elastomers, soft olefin polymers, andmixtures thereof.
 19. The method set forth in claim 18 wherein saidmatrix polymer material is a thermoplastic elastomer having a Shore Ahardness of 45 to 95 and flexural modulus of 30,000 to 100,000 psi. 20.The method set forth in claim 18 wherein said matrix polymer material isa thermoplastic elastomer selected from the group consisting of styreneblock copolymers and elastomeric alloys.
 21. The method set forth inclaim 18 wherein said matrix polymer material includes a olefin polymerthat is selected from the group consisting of metallocene-madepolyethylene, ethylene-propylene rubbers, ethylene copolymers, andmixtures thereof.
 22. The method set forth in claim 17 wherein saidbarrier polymer material is selected from the group consisting of EVOH,nylon, acrylonitrile copolymers, blends of EVOH and amorphous nylon,blends of EVOH and an ionomer, acrylonitrile, cyclic olefin copolymers,and blends thereof.
 23. The method set forth in claim 17 wherein saidstep (a) is such that said mold charge includes compatibilizer resinmaterial selected from the group consisting of maleic anhydride graftedpolymers, ethylene vinyl acetate grafted polymers, ethylene methylacrylate, ionomers and blends thereof.
 24. The method set forth in claim17 wherein said barrier polymer material comprises EVOH and said matrixpolymer material comprises EVA or polypropylene/butyl rubber.
 25. Themethod set forth in claim 17 wherein said barrier polymer material is inthe range of about 20% to 60% by weight, said compatibilizer resinmaterial is in the range of about 1% to 10% by weight, with the balanceconsisting of said matrix polymer material.
 26. The method set forth inclaim 17 wherein said platelets are substantially uniformly distributedthroughout said liner.
 27. The method set forth in claim 17 wherein saidliner contains lubricant in the amount of about 0.5% to 2.0% by weight.28. The method set forth in claim 27 wherein said lubricant is in theamount of about 1% by weight.
 29. The method set forth in claim 27wherein said lubricant is selected from the group consisting of fattyacid amides, fatty acid esters, microcrystalline waxes, polyethyleneglycols, primary amides, secondary amides, secondary-bis amides, andblends thereof.
 30. A method of making a liner for a plastic closurethat comprises the steps of: (a) forming a pellet that consistsessentially of a blend of matrix polymer material, barrier polymermaterial and compatibilizer resin material to promote adhesion betweenthe matrix polymer material and the barrier polymer material, and (b)compression molding said pellet to form a liner disk within which heatand pressure from compression molding form said barrier polymer materialinto discrete overlapping platelets that are oriented essentiallyparallel to the disk.
 31. The method set forth in claim 30 comprisingthe additional steps of: (c) providing a closure cap having a base and aperipheral skirt defining a cap interior and means on said skirt forsecuring the cap to a container, and (d) securing said liner disk to theinterior of said cap.
 32. The method set forth in claim 31 wherein saidsteps (b) and (d) are carried out simultaneously by compression moldingsaid pellet in situ on said base.
 33. The method set forth in claim 32wherein said step (a) comprises the step of forming said pellet suchthat said barrier material is substantially uniformly dispersed as adiscontinuous phase of discrete particles within said matrix material.34. The method set forth in claim 30 wherein said matrix polymermaterial is selected from the group consisting of thermoplasticelastomers, soft olefin polymers, and mixtures thereof.
 35. The methodset forth in claim 34 wherein said matrix polymer material is athermoplastic elastomer having a Shore A hardness of 45 to 95 and aflexural modulus of 30,000 to 100,000 psi.
 36. The method set forth inclaim 34 wherein said matrix polymer material is a thermoplasticelastomer selected from the group consisting of styrene block copolymersand elastomeric alloys.
 37. The method set forth in claim 34 whereinsaid matrix polymer material includes an olefin polymer selected fromthe group consisting of metallocene-made polyethylene,ethylene-propylene rubbers, ethylene copolymers, and mixtures thereof.38. The method set forth in claim 30 wherein said barrier polymermaterial is selected from the group consisting of EVOH, nylon,acrylonitrile copolymers, blends of EVOH and amorphous nylon, blends ofEVOH and an ionomer, acrylonitrile, cyclic olefin copolymers, and blendsthereof.
 39. The method set forth in claim 30 wherein compatibilizerresin material is selected from the group consisting of maleic anhydridegrafted polymers, ethylene vinyl acetate grafted polymers, ethylenemethyl acrylate, ionomers and blends thereof.
 40. The method set forthin claim 30 wherein said barrier polymer material comprises EVOH andsaid matrix material comprises EVA or polypropylene/butyl rubber. 41.The method set forth in claim 30 wherein said barrier polymer materialis in the range of about 20% to 60% by weight, said compatibilizer resinmaterial is in the range of about 1% to 10% by weight, with the balanceconsisting of said matrix polymer material.
 42. The method set forth inclaim 30 wherein said liner has a Shore A hardness of not more than 95.43. The method set forth in claim 30 wherein said liner containslubricant in the amount of about 0.5% to 2.0% by weight.
 44. The methodset forth in claim 43 wherein said lubricant is in the amount of about1% by weight.